There are generally known various kinds of methods for treating a stenosal portion of tubular organs of a living body such as an esophagus and the like without resort to a surgical operation. One of the known treatment methods is to use a self-expandable stent made of a super-elastic shape memory alloy. The term “stenosal portion” used herein refers to a bodily portion where stenosis is in progress or has been already completed.
In the stent-used treatment method, a cylindrical stent of specified length is formed by weaving super-elastic shape memory alloy wires. The stent is inserted into a stenosal portion of tubular organs of a living body with the volume thereof kept minimized. As the stent is set free and returned back to its original shape, the stenosal portion is expanded outwardly by the stent.
A separate stent inserting device is required in the stent-used treatment method in order to insert the stent into the stenosal portion of tubular organs. One example of conventional stent inserting devices is shown in FIG. 1. Referring to FIG. 1, the stent inserting device includes a grip body 2, an external tube 3 connected to the grip body 2 and an internal tube 5 inserted into the external tube 3 for movement in a forward or backward direction. A self-expandable stent 1 is slidably held within a tip end portion of the external tube 3 in a compressed state. The stent 1 is pushed out of the external tube 3 by means of the internal tube 5.
In the stent inserting device configured as above, the tip end portion of the external tube 3 in which the stent 1 is fitted in a compressed state is inserted into the stenosal portion of tubular organs of a living body such as an esophagus and the like. At this time, an endoscope is separately inserted to allow an operator to bring the tip end portion of the external tube 3 into a target position, i.e., in the stenosal portion of tubular organs, while observing the stent.
Once the tip end portion of the external tube 3 is inserted into the target position, the internal tube 5 is slidingly moved forward to push the stent 1 out of the tip end portion of the external tube 3. As illustrated in FIG. 2A, the leading end 1a of the stent 1 is first pushed out of the external tube 3 and expanded back to its original shape. In other words, the conventional stent inserting device is designed to ensure that the stent 1 is first expanded at its leading end 1a and then gradually expanded toward its trailing end 1b. When completely pushed out of the external tube 3, the stent 1 is capable of expanding the stenosal portion as shown in FIG. 2B.
In case a vocal cord or other membranes is situated behind the trailing end 1b of the stent 1, the conventional stent inserting device suffers from a problem in that the trailing end 1b of the stent 1 is caught by the vocal cord or other membranes in the process of expanding the stent 1 sequentially from the leading end toward the trailing end, which may cause the stent 1 to be situated in a wrong posture.
In particular, it is difficult to accurately estimate the position in which the trailing end 1b of the stent 1 lies when the stent 1 is fully expanded over the entire length thereof. This is because there is a great difference between the stent length available when the stent 1 is held within the tip end of the external tube 3 in a compressed state and the stent length available when the stent 1 is expanded back to its original shape in the stenosal portion.
Such problems posed in situating the stent 1 make it difficult for an operator to perform the stent inserting operation and also inflict physical or metal pains on a patient. In the worst circumstances, the stent inserting operation needs to be performed once again from the beginning.